A Century of Gravity

Category Archives: ESA

In this video, Günther Hasinger, ESA Director of Science, reflects on this historic measurement that inaugurated a century of exciting experiments, investigating gravity on Earth and in space and proving general relativity in ever greater detail. — NASA

ESA: As it scans the sky surveying stars in the Milky Way galaxy, Gaia has also detected a wealth of asteroids, the small rocky bodies that populate our solar system, mainly between the orbits of Mars and Jupiter. Because they are relatively nearby and orbiting the Sun, asteroids appear to move against the stars in astronomical images, appearing in one snapshot of a given field, but not in images of the same field taken at later times.

Gaia scientists have developed special software to look for these ‘outliers’, matching them with the orbits of known asteroids in order to remove them from the data being used to study stars. But in turn, this information will be used to characterise known asteroids and to discover thousands of new ones.

This image shows Gaia’s detections of asteroids in eight months’ worth of data, compared with the positions on the sky of a sample of 50 000 known asteroids. The colour of the data points is an indication of the accuracy of the detections, showing the separation on the sky between the observed position of Gaia’s detection and the expected position of each asteroid: blue indicates higher accuracy, whereas green and red indicate lower accuracy.

The regions showing lower accuracy of asteroid detections correspond to patches of the sky where the stellar density is very high, thus complicating the identification process.

Satellite marking could amount to much more than ESA describes in the press release going along with the picture above. I can see this being used for satellite recycling in the future.

ESA: Akin to landing lights for aircraft, ESA is developing infrared and phosphorescent markers for satellites, to help future space servicing vehicles rendezvous and dock with their targets.Developed by Hungarian company Admatis as part of an ESA Clean Space project, these markers would offer robotic space servicing vehicles a steady target to home in on, providing critical information on the line of sight, distance and pointing direction of their target satellite.Initial testing of these ‘Passive Emitting Material at end-of-life’ or PEMSUN markers took place at the end of March 2019 inside ESA’s GNC Rendezvous, Approach and Landing Simulator, part of the Agency’s Orbital Robotics and Guidance, Navigation and Control Laboratory, at its ESTEC technical centre in Noordwijk, the Netherlands.“The idea itself is not new, but this is the first time we’ve manufactured and tested sample patches, cut into spacecraft multi-layer insulation covering,” comments ESA Clean Space trainee Sébastien Perrault. “For the design we’ve looked into one larger pattern incorporating smaller versions for when the space servicing vehicle comes close enough that its camera’s field of view is filled.“These markers would be very useful during eclipse states for instance, when Earth obscures the Sun in low Earth orbit, to allow the chaser vehicle to stay fixed on its target, potentially in combination with radio tags.”ESA is studying space servicing vehicles to carry out a wide range of roles in orbit, from refurbishment and refuelling to mission disposal at their end of life.

The mission will study the Sun and solar wind but from very near our star and hopefully will begin to unlock some of the mystery of the solar corona among other things with the suite of instruments it is carrying on board.

ESA: An infrared view of our Solar Orbiter spacecraft, which is currently undergoing a series of tests at the IABG facility in Ottobrunn, Germany, ahead of its launch, scheduled for February 2020.

Selected in 2011 as the first medium-class mission in ESA’s Cosmic Vision programme, Solar Orbiter was designed to perform unprecedented close-up observations of the Sun. The spacecraft carries a suite of 10 state-of-the-art instruments to observe the turbulent, sometimes violent, surface of the Sun and study the changes that take place in the solar wind that flows outward at high speed from our nearest star.

Solar Orbiter’s unique orbit will allow scientists to study our parent star and its corona in much more detail than previously possible, and to observe specific features for longer periods than can ever be reached by any spacecraft circling the Earth. In addition, it will measure the solar wind close to the Sun, in an almost pristine state, and provide high-resolution images of the uncharted polar regions of the Sun.

After the preliminary definition and design phase, the mission started its integration and qualification in 2016, including environmental testing of the spacecraft as well as validation of all mission systems and sub-systems.

The first phase of Solar Orbiter’s environmental testing campaign was conducted in IABG’s special thermal-vacuum chamber in December 2018. Inside the chamber, powerful lamps are used to produce a ‘solar beam’ that simulates the Sun’s radiation to demonstrate that the spacecraft can sustain the extreme temperatures it will encounter in the Sun’s vicinity.

This picture was taken with an infrared camera, and the colouring indicates the temperatures of the spacecraft surface, corresponding to the range indicated in the colour bar on the right-hand side. During this thermal-vacuum test on the spacecraft, the solar beam was used at its maximum flux of about 1800 W/m2, reaching temperatures up to 107,6ºC. An additional thermal-vacuum test was conducted on the heat shield that protects the entire platform from direct solar radiation: during this test, which used infrared plates to simulate the Sun’s heat, the heat shield reached higher temperatures, up to 520ºC, similar to what it will experience during operations.

In this view, the spacecraft panel that will face the Sun is visible on the left, covered with the heat shield. The dark elements visible in the upper part of the panel are sliding doors that will open the path for sunlight to reach the remote-sensing instruments during science operations. Some of the thrusters that will be used to control the spacecraft orbit and to perform manoeuvres are hosted on the panel that is visible on the right in this view.

A video showing the spacecraft rotating as part of a simulated orbit-control-manoeuvre is available here.

After completing the thermal-vacuum tests, Solar Orbiter also successfully concluded the mechanical testing phase, including intense vibration tests, shaking the spacecraft to ensure that it will survive the stress of launch.

There has been a wonderful collection of images coming in from our Earth facing satellites lately. I like this one, even though I had the name wrong, calling it the Istanbul Strait at first glance. I was close though. This is the Bosphorus Strait.

ESA: Captured by the Copernicus Sentinel-1 mission, this image shows the narrow strait that connects eastern Europe to western Asia: the Bosphorus in northwest Turkey. The image contains satellite data stitched together from three radar scans acquired on 2 June, 8 July and 13 August 2018.

Separating the Black Sea and the Sea of Marmara, the strait is one of the busiest maritime passages in the world, with around 48 000 ships passing through every year. Daily traffic includes international commercial shipping vessels and oil tankers, as well as local fishing and ferries. Ships in the strait can be seen in the image as multi-coloured dots. Three bridges are also visible spanning the strait and connecting the two continents.

The two identical Copernicus Sentinel-1 satellites carry radar instruments, which can see through clouds and rain, and in the dark, to image Earth’s surface below. The multi-temporal remote sensing technique combines two or more radar images over the same area to detect changes occurring between acquisitions.

In the far-left of this image, the aqua-green patches of land show the changes in the fields between the three satellite acquisitions.

Turkey’s most populous city, Istanbul, can be seen on both sides of the Bosphorus. The city appears in shades of white owing to the stronger reflection of the radar signal from buildings, which contrasts with the dark black colour of the inland lakes and surrounding waters.

The JUICE spacecraft is taking shape and the magnetometer boom is being tested in an innovative way.

ESA: A test version of the 10.5-m long magnetometer boom built for ESA’s mission to Jupiter, developed by SENER in Spain, seen being tested at ESA’s Test Centre in the Netherlands, its weight borne by balloons.

The flight model will be mounted on the Juice spacecraft – Jupiter Icy Moons Explorer – due to launch in 2022, arriving at Jupiter in 2029. The mission will spend at least three years making detailed observations of the giant gaseous planet Jupiter and three of its largest moons: Ganymede, Callisto and Europa.

The Juice spacecraft will carry the most powerful remote sensing, geophysical, and in situ payload complement ever flown to the outer Solar System. Its payload consists of 10 state-of-the-art instruments.

This includes a magnetometer instrument that the boom will project clear of the main body of the spacecraft, allowing it to make measurements clear of any magnetic interference. Its goal is to measure Jupiter’s magnetic field, its interaction with the internal magnetic field of Ganymede, and to study subsurface oceans of the icy moons.

The deployment of this qualification model boom has been performed before and after simulated launch vibration on Test Centre shaker tables to ensure it will deploy correctly in space. Since the boom will deploy in weightlessness, three helium balloons were used to help bear its weight in terrestrial gravity.

CHEOPS or Characterising Exoplanet Satellite is steadily moving towards a launch date later this year. Currently the satellite is at Airbus Defence and Space Spain, Madrid and will eventually be shipped to Kourou, French Guiana for launch.